Use the Figure and the Following Description to Answer the Question

Multiple Choice

Use the figure and the following description to answer the question.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes marked 1-4 correspond to plants that will be true-breeding?

A) 1 and 4 only
B) 2 and 3 only
C) 1, 2, 3, and 4
D) 1 only